package com.season.seasonStudy.hashmap;

import java.io.IOException;
import java.util.*;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Consumer;

/**
     * <p>Hash table and linked list implementation of the <tt>Map</tt> interface,
     * with predictable iteration order.  This implementation differs from
     * <tt>SeasonHashMap</tt> in that it maintains a doubly-linked list running through
     * all of its entries.  This linked list defines the iteration ordering,
     * which is normally the order in which keys were inserted into the map
     * (<i>insertion-order</i>).  Note that insertion order is not affected
     * if a key is <i>re-inserted</i> into the map.  (A key <tt>k</tt> is
     * reinserted into a map <tt>m</tt> if <tt>m.put(k, v)</tt> is invoked when
     * <tt>m.containsKey(k)</tt> would return <tt>true</tt> immediately prior to
     * the invocation.)
     *
     * <p>This implementation spares its clients from the unspecified, generally
     * chaotic ordering provided by {@link SeasonHashMap} (and {@link Hashtable}),
     * without incurring the increased cost associated with {@link TreeMap}.  It
     * can be used to produce a copy of a map that has the same order as the
     * original, regardless of the original map's implementation:
     * <pre>
     *     void foo(Map m) {
     *         Map copy = new LinkedHashMapTemp(m);
     *         ...
     *     }
     * </pre>
     * This technique is particularly useful if a module takes a map on input,
     * copies it, and later returns results whose order is determined by that of
     * the copy.  (Clients generally appreciate having things returned in the same
     * order they were presented.)
     *
     * <p>A special {@link #LinkedHashMapTemp(int,float,boolean) constructor} is
     * provided to create a linked hash map whose order of iteration is the order
     * in which its entries were last accessed, from least-recently accessed to
     * most-recently (<i>access-order</i>).  This kind of map is well-suited to
     * building LRU caches.  Invoking the {@code put}, {@code putIfAbsent},
     * {@code get}, {@code getOrDefault}, {@code compute}, {@code computeIfAbsent},
     * {@code computeIfPresent}, or {@code merge} methods results
     * in an access to the corresponding entry (assuming it exists after the
     * invocation completes). The {@code replace} methods only result in an access
     * of the entry if the value is replaced.  The {@code putAll} method generates one
     * entry access for each mapping in the specified map, in the order that
     * key-value mappings are provided by the specified map's entry set iterator.
     * <i>No other methods generate entry accesses.</i>  In particular, operations
     * on collection-views do <i>not</i> affect the order of iteration of the
     * backing map.
     *
     * <p>The {@link #removeEldestEntry(Map.Entry)} method may be overridden to
     * impose a policy for removing stale mappings automatically when new mappings
     * are added to the map.
     *
     * <p>This class provides all of the optional <tt>Map</tt> operations, and
     * permits null elements.  Like <tt>SeasonHashMap</tt>, it provides constant-time
     * performance for the basic operations (<tt>add</tt>, <tt>contains</tt> and
     * <tt>remove</tt>), assuming the hash function disperses elements
     * properly among the buckets.  Performance is likely to be just slightly
     * below that of <tt>SeasonHashMap</tt>, due to the added expense of maintaining the
     * linked list, with one exception: Iteration over the collection-views
     * of a <tt>LinkedHashMapTemp</tt> requires time proportional to the <i>size</i>
     * of the map, regardless of its capacity.  Iteration over a <tt>SeasonHashMap</tt>
     * is likely to be more expensive, requiring time proportional to its
     * <i>capacity</i>.
     *
     * <p>A linked hash map has two parameters that affect its performance:
     * <i>initial capacity</i> and <i>load factor</i>.  They are defined precisely
     * as for <tt>SeasonHashMap</tt>.  Note, however, that the penalty for choosing an
     * excessively high value for initial capacity is less severe for this class
     * than for <tt>SeasonHashMap</tt>, as iteration times for this class are unaffected
     * by capacity.
     *
     * <p><strong>Note that this implementation is not synchronized.</strong>
     * If multiple threads access a linked hash map concurrently, and at least
     * one of the threads modifies the map structurally, it <em>must</em> be
     * synchronized externally.  This is typically accomplished by
     * synchronizing on some object that naturally encapsulates the map.
     *
     * If no such object exists, the map should be "wrapped" using the
     * {@link Collections#synchronizedMap Collections.synchronizedMap}
     * method.  This is best done at creation time, to prevent accidental
     * unsynchronized access to the map:<pre>
     *   Map m = Collections.synchronizedMap(new LinkedHashMapTemp(...));</pre>
     *
     * A structural modification is any operation that adds or deletes one or more
     * mappings or, in the case of access-ordered linked hash maps, affects
     * iteration order.  In insertion-ordered linked hash maps, merely changing
     * the value associated with a key that is already contained in the map is not
     * a structural modification.  <strong>In access-ordered linked hash maps,
     * merely querying the map with <tt>get</tt> is a structural modification.
     * </strong>)
     *
     * <p>The iterators returned by the <tt>iterator</tt> method of the collections
     * returned by all of this class's collection view methods are
     * <em>fail-fast</em>: if the map is structurally modified at any time after
     * the iterator is created, in any way except through the iterator's own
     * <tt>remove</tt> method, the iterator will throw a {@link
     * ConcurrentModificationException}.  Thus, in the face of concurrent
     * modification, the iterator fails quickly and cleanly, rather than risking
     * arbitrary, non-deterministic behavior at an undetermined time in the future.
     *
     * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
     * as it is, generally speaking, impossible to make any hard guarantees in the
     * presence of unsynchronized concurrent modification.  Fail-fast iterators
     * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
     * Therefore, it would be wrong to write a program that depended on this
     * exception for its correctness:   <i>the fail-fast behavior of iterators
     * should be used only to detect bugs.</i>
     *
     * <p>The spliterators returned by the spliterator method of the collections
     * returned by all of this class's collection view methods are
     * <em><a href="Spliterator.html#binding">late-binding</a></em>,
     * <em>fail-fast</em>, and additionally report {@link Spliterator#ORDERED}.
     *
     * <p>This class is a member of the
     * <a href="{@docRoot}/../technotes/guides/collections/index.html">
     * Java Collections Framework</a>.
     *
     * @implNote
     * The spliterators returned by the spliterator method of the collections
     * returned by all of this class's collection view methods are created from
     * the iterators of the corresponding collections.
     *
     * @param <K> the type of keys maintained by this map
     * @param <V> the type of mapped values
     *
     * @author  Josh Bloch
     * @see     Object#hashCode()
     * @see     Collection
     * @see     Map
     * @see     SeasonHashMap
     * @see     TreeMap
     * @see     Hashtable
     * @since   1.4
     */
    public class LinkedHashMapTemp<K,V>
            extends SeasonHashMap<K,V>
            implements Map<K,V>
    {

        /*
         * Implementation note.  A previous version of this class was
         * internally structured a little differently. Because superclass
         * SeasonHashMap now uses trees for some of its nodes, class
         * LinkedHashMapTemp.Entry is now treated as intermediary node class
         * that can also be converted to tree form. The name of this
         * class, LinkedHashMapTemp.Entry, is confusing in several ways in its
         * current context, but cannot be changed.  Otherwise, even though
         * it is not exported outside this package, some existing source
         * code is known to have relied on a symbol resolution corner case
         * rule in calls to removeEldestEntry that suppressed compilation
         * errors due to ambiguous usages. So, we keep the name to
         * preserve unmodified compilability.
         *
         * The changes in node classes also require using two fields
         * (head, tail) rather than a pointer to a header node to maintain
         * the doubly-linked before/after list. This class also
         * previously used a different style of callback methods upon
         * access, insertion, and removal.
         */

        /**
         * SeasonHashMap.Node subclass for normal LinkedHashMapTemp entries.
         */
        static class Entry<K,V> extends SeasonHashMap.Node<K,V> {
            Entry<K,V> before, after;
            Entry(int hash, K key, V value, SeasonHashMap.Node<K,V> next) {
                super(hash, key, value, next);
            }
        }

        private static final long serialVersionUID = 3801124242820219131L;

        /**
         * The head (eldest) of the doubly linked list.
         */
        transient Entry<K,V> head;

        /**
         * The tail (youngest) of the doubly linked list.
         */
        transient Entry<K,V> tail;

        /**
         * The iteration ordering method for this linked hash map: <tt>true</tt>
         * for access-order, <tt>false</tt> for insertion-order.
         *
         * @serial
         */
        final boolean accessOrder;

        // internal utilities

        // link at the end of list
        private void linkNodeLast(Entry<K,V> p) {
            Entry<K,V> last = tail;
            tail = p;
            if (last == null)
                head = p;
            else {
                p.before = last;
                last.after = p;
            }
        }

        // apply src's links to dst
        private void transferLinks(Entry<K,V> src,
                                   Entry<K,V> dst) {
            Entry<K,V> b = dst.before = src.before;
            Entry<K,V> a = dst.after = src.after;
            if (b == null)
                head = dst;
            else
                b.after = dst;
            if (a == null)
                tail = dst;
            else
                a.before = dst;
        }

        // overrides of SeasonHashMap hook methods

        void reinitialize() {
            super.reinitialize();
            head = tail = null;
        }

        SeasonHashMap.Node<K,V> newNode(int hash, K key, V value, SeasonHashMap.Node<K,V> e) {
            Entry<K,V> p =
                    new Entry<K,V>(hash, key, value, e);
            linkNodeLast(p);
            return p;
        }

        SeasonHashMap.Node<K,V> replacementNode(SeasonHashMap.Node<K,V> p, SeasonHashMap.Node<K,V> next) {
            Entry<K,V> q = (Entry<K,V>)p;
            Entry<K,V> t =
                    new Entry<K,V>(q.hash, q.key, q.value, next);
            transferLinks(q, t);
            return t;
        }

        TreeNode<K,V> newTreeNode(int hash, K key, V value, SeasonHashMap.Node<K,V> next) {
            TreeNode<K,V> p = new TreeNode<K,V>(hash, key, value, next);
            linkNodeLast(p);
            return p;
        }

        TreeNode<K,V> replacementTreeNode(SeasonHashMap.Node<K,V> p, SeasonHashMap.Node<K,V> next) {
            Entry<K,V> q = (Entry<K,V>)p;
            TreeNode<K,V> t = new TreeNode<K,V>(q.hash, q.key, q.value, next);
            transferLinks(q, t);
            return t;
        }

        void afterNodeRemoval(SeasonHashMap.Node<K,V> e) { // unlink
            Entry<K,V> p =
                    (Entry<K,V>)e, b = p.before, a = p.after;
            p.before = p.after = null;
            if (b == null)
                head = a;
            else
                b.after = a;
            if (a == null)
                tail = b;
            else
                a.before = b;
        }

        void afterNodeInsertion(boolean evict) { // possibly remove eldest
            Entry<K,V> first;
            if (evict && (first = head) != null && removeEldestEntry(first)) {
                K key = first.key;
                removeNode(hash(key), key, null, false, true);
            }
        }

        void afterNodeAccess(SeasonHashMap.Node<K,V> e) { // move node to last
            Entry<K,V> last;
            if (accessOrder && (last = tail) != e) { // accessOrder，访问顺序，当前节点被访问了，需要放在最后面，维护节点的访问顺序
                Entry<K,V> p =
                        (Entry<K,V>)e, b = p.before, a = p.after;
                p.after = null;
                if (b == null) // 将当前p移出
                    head = a;
                else
                    b.after = a;
                if (a != null)
                    a.before = b;
                else
                    last = b;
                if (last == null)
                    head = p;
                else {
                    p.before = last;
                    last.after = p;
                }
                tail = p;
                ++modCount;
            }
        }

        void internalWriteEntries(java.io.ObjectOutputStream s) throws IOException {
            for (Entry<K,V> e = head; e != null; e = e.after) {
                s.writeObject(e.key);
                s.writeObject(e.value);
            }
        }

        /**
         * Constructs an empty insertion-ordered <tt>LinkedHashMapTemp</tt> instance
         * with the specified initial capacity and load factor.
         *
         * @param  initialCapacity the initial capacity
         * @param  loadFactor      the load factor
         * @throws IllegalArgumentException if the initial capacity is negative
         *         or the load factor is nonpositive
         */
        public LinkedHashMapTemp(int initialCapacity, float loadFactor) {
            super(initialCapacity, loadFactor);
            accessOrder = false;
        }

        /**
         * Constructs an empty insertion-ordered <tt>LinkedHashMapTemp</tt> instance
         * with the specified initial capacity and a default load factor (0.75).
         *
         * @param  initialCapacity the initial capacity
         * @throws IllegalArgumentException if the initial capacity is negative
         */
        public LinkedHashMapTemp(int initialCapacity) {
            super(initialCapacity);
            accessOrder = false;
        }

        /**
         * Constructs an empty insertion-ordered <tt>LinkedHashMapTemp</tt> instance
         * with the default initial capacity (16) and load factor (0.75).
         */
        public LinkedHashMapTemp() {
            super();
            accessOrder = false;
        }

        /**
         * Constructs an insertion-ordered <tt>LinkedHashMapTemp</tt> instance with
         * the same mappings as the specified map.  The <tt>LinkedHashMapTemp</tt>
         * instance is created with a default load factor (0.75) and an initial
         * capacity sufficient to hold the mappings in the specified map.
         *
         * @param  m the map whose mappings are to be placed in this map
         * @throws NullPointerException if the specified map is null
         */
        public LinkedHashMapTemp(Map<? extends K, ? extends V> m) {
            super();
            accessOrder = false;
            putMapEntries(m, false);
        }

        /**
         * Constructs an empty <tt>LinkedHashMapTemp</tt> instance with the
         * specified initial capacity, load factor and ordering mode.
         *
         * @param  initialCapacity the initial capacity
         * @param  loadFactor      the load factor
         * @param  accessOrder     the ordering mode - <tt>true</tt> for
         *         access-order, <tt>false</tt> for insertion-order
         * @throws IllegalArgumentException if the initial capacity is negative
         *         or the load factor is nonpositive
         */
        public LinkedHashMapTemp(int initialCapacity,
                                 float loadFactor,
                                 boolean accessOrder) {
            super(initialCapacity, loadFactor);
            this.accessOrder = accessOrder;
        }


        /**
         * Returns <tt>true</tt> if this map maps one or more keys to the
         * specified value.
         *
         * @param value value whose presence in this map is to be tested
         * @return <tt>true</tt> if this map maps one or more keys to the
         *         specified value
         */
        public boolean containsValue(Object value) {
            for (Entry<K,V> e = head; e != null; e = e.after) {
                V v = e.value;
                if (v == value || (value != null && value.equals(v)))
                    return true;
            }
            return false;
        }

        /**
         * Returns the value to which the specified key is mapped,
         * or {@code null} if this map contains no mapping for the key.
         *
         * <p>More formally, if this map contains a mapping from a key
         * {@code k} to a value {@code v} such that {@code (key==null ? k==null :
         * key.equals(k))}, then this method returns {@code v}; otherwise
         * it returns {@code null}.  (There can be at most one such mapping.)
         *
         * <p>A return value of {@code null} does not <i>necessarily</i>
         * indicate that the map contains no mapping for the key; it's also
         * possible that the map explicitly maps the key to {@code null}.
         * The {@link #containsKey containsKey} operation may be used to
         * distinguish these two cases.
         */
        public V get(Object key) {
            SeasonHashMap.Node<K,V> e;
            if ((e = getNode(hash(key), key)) == null)
                return null;
            if (accessOrder)
                afterNodeAccess(e);
            return e.value;
        }

        /**
         * {@inheritDoc}
         */
        public V getOrDefault(Object key, V defaultValue) {
            SeasonHashMap.Node<K,V> e;
            if ((e = getNode(hash(key), key)) == null)
                return defaultValue;
            if (accessOrder)
                afterNodeAccess(e);
            return e.value;
        }

        /**
         * {@inheritDoc}
         */
        public void clear() {
            super.clear();
            head = tail = null;
        }

        /**
         * Returns <tt>true</tt> if this map should remove its eldest entry.
         * This method is invoked by <tt>put</tt> and <tt>putAll</tt> after
         * inserting a new entry into the map.  It provides the implementor
         * with the opportunity to remove the eldest entry each time a new one
         * is added.  This is useful if the map represents a cache: it allows
         * the map to reduce memory consumption by deleting stale entries.
         *
         * <p>Sample use: this override will allow the map to grow up to 100
         * entries and then delete the eldest entry each time a new entry is
         * added, maintaining a steady state of 100 entries.
         * <pre>
         *     private static final int MAX_ENTRIES = 100;
         *
         *     protected boolean removeEldestEntry(Map.Entry eldest) {
         *        return size() &gt; MAX_ENTRIES;
         *     }
         * </pre>
         *
         * <p>This method typically does not modify the map in any way,
         * instead allowing the map to modify itself as directed by its
         * return value.  It <i>is</i> permitted for this method to modify
         * the map directly, but if it does so, it <i>must</i> return
         * <tt>false</tt> (indicating that the map should not attempt any
         * further modification).  The effects of returning <tt>true</tt>
         * after modifying the map from within this method are unspecified.
         *
         * <p>This implementation merely returns <tt>false</tt> (so that this
         * map acts like a normal map - the eldest element is never removed).
         *
         * @param    eldest The least recently inserted entry in the map, or if
         *           this is an access-ordered map, the least recently accessed
         *           entry.  This is the entry that will be removed it this
         *           method returns <tt>true</tt>.  If the map was empty prior
         *           to the <tt>put</tt> or <tt>putAll</tt> invocation resulting
         *           in this invocation, this will be the entry that was just
         *           inserted; in other words, if the map contains a single
         *           entry, the eldest entry is also the newest.
         * @return   <tt>true</tt> if the eldest entry should be removed
         *           from the map; <tt>false</tt> if it should be retained.
         */
        protected boolean removeEldestEntry(Map.Entry<K,V> eldest) {
            return false;
        }

        /**
         * Returns a {@link Set} view of the keys contained in this map.
         * The set is backed by the map, so changes to the map are
         * reflected in the set, and vice-versa.  If the map is modified
         * while an iteration over the set is in progress (except through
         * the iterator's own <tt>remove</tt> operation), the results of
         * the iteration are undefined.  The set supports element removal,
         * which removes the corresponding mapping from the map, via the
         * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
         * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
         * operations.  It does not support the <tt>add</tt> or <tt>addAll</tt>
         * operations.
         * Its {@link Spliterator} typically provides faster sequential
         * performance but much poorer parallel performance than that of
         * {@code SeasonHashMap}.
         *
         * @return a set view of the keys contained in this map
         */
        public Set<K> keySet() {
            Set<K> ks = keySet;
            if (ks == null) {
                ks = new LinkedKeySetTemp();
                keySet = ks;
            }
            return ks;
        }

        final class LinkedKeySetTemp extends AbstractSetTemp<K> {
            public final int size()                 { return size; }
            public final void clear()               { this.clear(); }
            public final Iterator<K> iterator() {
                return new LinkedKeyIterator();
            }
            public final boolean contains(Object o) { return containsKey(o); }
            public final boolean remove(Object key) {
                return removeNode(hash(key), key, null, false, true) != null;
            }
            public final Spliterator<K> spliterator()  {
                return Spliterators.spliterator(this, Spliterator.SIZED |
                        Spliterator.ORDERED |
                        Spliterator.DISTINCT);
            }
            public final void forEach(Consumer<? super K> action) {
                if (action == null)
                    throw new NullPointerException();
                int mc = modCount;
                for (Entry<K,V> e = head; e != null; e = e.after)
                    action.accept(e.key);
                if (modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }

        /**
         * Returns a {@link Collection} view of the values contained in this map.
         * The collection is backed by the map, so changes to the map are
         * reflected in the collection, and vice-versa.  If the map is
         * modified while an iteration over the collection is in progress
         * (except through the iterator's own <tt>remove</tt> operation),
         * the results of the iteration are undefined.  The collection
         * supports element removal, which removes the corresponding
         * mapping from the map, via the <tt>Iterator.remove</tt>,
         * <tt>Collection.remove</tt>, <tt>removeAll</tt>,
         * <tt>retainAll</tt> and <tt>clear</tt> operations.  It does not
         * support the <tt>add</tt> or <tt>addAll</tt> operations.
         * Its {@link Spliterator} typically provides faster sequential
         * performance but much poorer parallel performance than that of
         * {@code SeasonHashMap}.
         *
         * @return a view of the values contained in this map
         */
        public Collection<V> values() {
            Collection<V> vs = values;
            if (vs == null) {
                vs = new LinkedValues();
                values = vs;
            }
            return vs;
        }

        final class LinkedValues extends AbstractCollection<V> {
            public final int size()                 { return size; }
            public final void clear()               { this.clear(); }
            public final Iterator<V> iterator() {
                return new LinkedValueIterator();
            }
            public final boolean contains(Object o) { return containsValue(o); }
            public final Spliterator<V> spliterator() {
                return Spliterators.spliterator(this, Spliterator.SIZED |
                        Spliterator.ORDERED);
            }
            public final void forEach(Consumer<? super V> action) {
                if (action == null)
                    throw new NullPointerException();
                int mc = modCount;
                for (Entry<K,V> e = head; e != null; e = e.after)
                    action.accept(e.value);
                if (modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }

        /**
         * Returns a {@link Set} view of the mappings contained in this map.
         * The set is backed by the map, so changes to the map are
         * reflected in the set, and vice-versa.  If the map is modified
         * while an iteration over the set is in progress (except through
         * the iterator's own <tt>remove</tt> operation, or through the
         * <tt>setValue</tt> operation on a map entry returned by the
         * iterator) the results of the iteration are undefined.  The set
         * supports element removal, which removes the corresponding
         * mapping from the map, via the <tt>Iterator.remove</tt>,
         * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
         * <tt>clear</tt> operations.  It does not support the
         * <tt>add</tt> or <tt>addAll</tt> operations.
         * Its {@link Spliterator} typically provides faster sequential
         * performance but much poorer parallel performance than that of
         * {@code SeasonHashMap}.
         *
         * @return a set view of the mappings contained in this map
         */
        public Set<Map.Entry<K,V>> entrySet() {
            Set<Map.Entry<K,V>> es;
            return (es = entrySet) == null ? (entrySet = new LinkedEntrySetTemp()) : es;
        }

        final class LinkedEntrySetTemp extends AbstractSetTemp<Map.Entry<K,V>> {
            public final int size()                 { return size; }
            public final void clear()               { this.clear(); }
            public final Iterator<Map.Entry<K,V>> iterator() {
                return new LinkedEntryIterator();
            }
            public final boolean contains(Object o) {
                if (!(o instanceof Map.Entry))
                    return false;
                Map.Entry<?,?> e = (Map.Entry<?,?>) o;
                Object key = e.getKey();
                SeasonHashMap.Node<K,V> candidate = getNode(hash(key), key);
                return candidate != null && candidate.equals(e);
            }
            public final boolean remove(Object o) {
                if (o instanceof Map.Entry) {
                    Map.Entry<?,?> e = (Map.Entry<?,?>) o;
                    Object key = e.getKey();
                    Object value = e.getValue();
                    return removeNode(hash(key), key, value, true, true) != null;
                }
                return false;
            }
            public final Spliterator<Map.Entry<K,V>> spliterator() {
                return Spliterators.spliterator(this, Spliterator.SIZED |
                        Spliterator.ORDERED |
                        Spliterator.DISTINCT);
            }
            public final void forEach(Consumer<? super Map.Entry<K,V>> action) {
                if (action == null)
                    throw new NullPointerException();
                int mc = modCount;
                for (Entry<K,V> e = head; e != null; e = e.after)
                    action.accept(e);
                if (modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }

        // Map overrides

        public void forEach(BiConsumer<? super K, ? super V> action) {
            if (action == null)
                throw new NullPointerException();
            int mc = modCount;
            for (Entry<K,V> e = head; e != null; e = e.after)
                action.accept(e.key, e.value);
            if (modCount != mc)
                throw new ConcurrentModificationException();
        }

        public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
            if (function == null)
                throw new NullPointerException();
            int mc = modCount;
            for (Entry<K,V> e = head; e != null; e = e.after)
                e.value = function.apply(e.key, e.value);
            if (modCount != mc)
                throw new ConcurrentModificationException();
        }

        // Iterators

        abstract class LinkedHashIterator {
            Entry<K,V> next;
            Entry<K,V> current;
            int expectedModCount;

            LinkedHashIterator() {
                next = head;
                expectedModCount = modCount;
                current = null;
            }

            public final boolean hasNext() {
                return next != null;
            }

            final Entry<K,V> nextNode() {
                Entry<K,V> e = next;
                if (modCount != expectedModCount)
                    throw new ConcurrentModificationException();
                if (e == null)
                    throw new NoSuchElementException();
                current = e;
                next = e.after;
                return e;
            }

            public final void remove() {
                SeasonHashMap.Node<K,V> p = current;
                if (p == null)
                    throw new IllegalStateException();
                if (modCount != expectedModCount)
                    throw new ConcurrentModificationException();
                current = null;
                K key = p.key;
                removeNode(hash(key), key, null, false, false);
                expectedModCount = modCount;
            }
        }

        final class LinkedKeyIterator extends LinkedHashIterator
                implements Iterator<K> {
            public final K next() { return nextNode().getKey(); }
        }

        final class LinkedValueIterator extends LinkedHashIterator
                implements Iterator<V> {
            public final V next() { return nextNode().value; }
        }

        final class LinkedEntryIterator extends LinkedHashIterator
                implements Iterator<Map.Entry<K,V>> {
            public final Map.Entry<K,V> next() { return nextNode(); }
        }


    }
